Numerous applications require the provision of a seal between two elements that rotate relative to one another and between which it must be possible to establish one or more highly pressurized hydraulic fluid or gaseous flows via ducts arranged accordingly within each of said elements.
One application lies, for example, in feeding hydraulic fluid—from a stator—to cylinders arranged in the rotor of a hydraulic pump having high-pressure rotating pistons. With regard to said application and in accordance with a particular embodiment, the same rotating sealing coupling may have an inflow duct and an outflow duct in order to allow said fluid to enter said rotor at low pressure then to leave said rotor at high pressure by the same aforesaid coupling.
By way of example, a rotating sealing coupling can be used in certain hydraulic clutches, said coupling having only a single duct, which ensures both the inflow and the outflow of the hydraulic fluid.
Lastly, numerous industrial and domestic applications require the implementation of one or more rotating couplings in the high-pressure field, such as those sold by the company “Duff-Norton”.
The seal of these couplings is most often ensured by a contact pressure provided between the elements rotating relative to one another, moreover by means of materials that are resistant to abrasion and known to have a reduced coefficient of friction, such as carbon graphite, ceramic, tungsten carbide or polytetrafluoroethylene, referred to as “PTFE” or “Teflon”. Said materials are selected in particular under consideration of the fluid to be sealed, depending on whether this is liquid or gaseous, and depending on the degree of corrosivity of said fluid.
Since said materials are generally subjected to high contact pressures and to elevated sliding speeds, their service life is limited to the point that it may be necessary to change them regularly and that their speed of rotation is limited, as is their service pressure, which rarely exceeds 1000 bar.
It is thus clear that it is difficult to design and provide rotating sealing couplings operating in the field of very high pressures (of approximately 1000 bar or up to 2000 bar and more) which are sufficiently tight and durable so as to avoid maintenance, and which can operate at high speeds of rotation whilst remaining compact, economical and poor dissipaters of frictional energy.
It is noted that various applications will experience a significant increase in efficacy by such couplings, such as the hydraulic pump/motor with fixed or variable cylinder forming the basis of patent application no. FR 1354562 dated 22 May 2013 and filed by the applicant.